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The History of the Microscope
Nature Bulletin No. 506 November 9, 1957
Forest Preserve District of Cook County
Daniel Ryan, President
Roberts Mann, Conservation Editor
David H. Thompson, Senior Naturalist
THE HISTORY OF THE MICROSCOPE
During that historic period known as the Renaissance, after the "dark"
Middle Ages, there occurred the inventions of printing, gunpowder and
the mariner's compass, followed by the discovery of America. Equally
remarkable was the invention of the microscope: an instrument that
enables the human eye, by means of a lens or combinations of lenses, to
observe enlarged images of tiny objects. It made visible the fascinating
details of worlds within worlds.
Long before, in the hazy unrecorded past, someone picked up a piece of
transparent crystal thicker in the middle than at the edges, looked
through it, and discovered that it made things look larger. Someone also
found that such a crystal would focus the sun's rays and set fire to a
piece of parchment or cloth. Magnifiers and "burning glasses" are
mentioned in the writings of Seneca and Pliny the Elder, Roman
philosophers during the first century A. D., but apparently they were not
used much until the invention of spectacles, toward the end of the 13th
century. They were named lenses because they are shaped like the seeds
of a lentil.
The earliest simple microscope was merely a tube with a plate for the
object at one end and, at the other, a lens which gave a magnification
less than ten diameters -- ten times the actual size. These excited
general wonder when used to view fleas or tiny creeping things and so
were dubbed "flea glasses. "
About 1590, two Dutch spectacle-makers, Zaccharias Janssen and his
son Hans, while experimenting with several lenses in a tube, discovered
that nearby objects appeared greatly enlarged. That was the forerunner
of the compound microscope and of the telescope. In 1609 Galileo,
father of modern physics and astronomy, heard of these early
experiments, worked out the principles of lenses, and made a much
better instrument with a focusing device.
The father of microscopy, Anthony Leeuwenhoek of Holland
(1632-1723), started as an apprentice in a dry goods store where
magnifying glasses were used to count the threads in cloth. He taught
himself new methods for grinding and polishing tiny lenses of great
curvature which gave magnifications up to 270 diameters, the finest
known at that time. These led to the building of his microscopes and the
biological discoveries for which he is famous. He was the first to see
and describe bacteria, yeast plants, the teeming life in a drop of water,
and the circulation of blood corpuscles in capillaries. During a long life
he used his lenses to make pioneer studies on an extraordinary variety
of things, both living and non-living, and reported his findings in over a
hundred letters to the Royal Society of England and the French
Academy.
Few
major improvements were made until the middle of the 19th
century. Then several European countries began to manufacture fine
optical equipment but none finer than the marvelous microscopes built
by the American, Charles A. Spencer, and the industry he founded.
Present day instruments, changed but little, give magnifications up to
1250 diameters with ordinary light and up to 5000 with blue light.
As late as the 70's and 80's, only a few doctors and college professors
owned a microscope. Today they are an essential tool in every high
school, college, hospital, and research laboratory. To meet the special
needs of scientists and industries, startling variations have been devised
-- the electron microscope, the x-ray microscope and several others --
which enable man to view or photograph matter of molecular and even
atomic dimensions.
A hand lens will reveal fascinating new worlds to a youngster.
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